1. Field of the Invention
This invention relates to a xerographic apparatus for a label printer, more particularly to such an apparatus which uses a continuous label strip comprising a backing sheet having a series of labels provisionally attached thereto, and still more particularly to such an apparatus which eliminates any slack arising in the continuous label strip ahead of the toner fixing section.
2. Description of the Prior Art
For labeling purposes there is commonly used a continuous label strip fabricated by trimming labels obtained from a label sheet into an appropriate shape and then provisionally attaching them serially at appropriate intervals to the side of a backing strip which has been coated with a release agent. While the printing of the required information onto the labels has most often been conducted by use of a thermal printer, xerographic printing apparatus have also recently come into use.
Although the individual labels are separated from each other by creases, they are in some cases provisionally attached to the backing strip without any interval therebetween, whereas in other cases labels trimmed from label sheets and removed of the trimmed scraps are provisionally attached at prescribed intervals. This latter type of continuous label strip is widely used because of such various advantages such as that the labels can be freely designed to have rounded corners or to be circular, triangular, hexagonal, flower shaped or the like, that the label strip has regions with different transmittance which can be used for detecting the label pitch (the interval at which the labels are provisionally attached to the backing strip) without need for affixing any other special mark or the like, and that the labels are easy to detach from the backing strip.
Referring to FIG. 1, in a continuous label strip A consisting of labels L cut from a label sheet attached at prescribed intervals to a backing strip S, the regions D of the backing strip S not overlaid with labels L are generally exposed in their state as coated with a silicon-based release agent. The thickness of the continuous label strip A is thus different between these regions D and the regions where the labels L are overlaid on the backing strip S.
Where a xerographic apparatus is used, the peripheral speed of its photosensitive drum and that of the toner fixing section are precisely the same and become the conveyance speed of the continuous label strip A.
When label printing is conducted with a continuous label strip A of the foregoing type loaded in the conventional xerographic apparatus, slippage occurs between the rollers at the toner fixing section and the continuous label strip A passing therethrough because of the lower coefficient of friction of the regions D coated with the exposed release agent and at the transition regions between the regions where the labels L are overlaid on the backing strip S and the regions D consisting solely of the backing strip S, which leads to slippage in the conveyance of the continuous label strip A at the toner fixing section.
As a result, the conveyance rate of the continuous label strip becomes lower at the toner fixing section than at the photosensitive drum, which causes the portion of the continuous label strip ahead of the toner fixing section to be come slack. In the case of continuous printing or the like, the amount of this slack progressively accrues and becomes a cause for jamming.